Tools / DNS lookup
DNS lookup
What each DNS record does
DNS turns a name into the places its services live. When a website, email or certificate breaks after a change, the records below are usually the reason.
- A and AAAA
- The IPv4 and IPv6 addresses of the server. Point these at your host to move a site.
- CNAME
- An alias to another name. Common for www and for services such as CDNs.
- MX
- Where email for the domain is delivered, in order of priority. The lowest number is tried first.
- TXT
- Verification codes and email security: SPF lists who may send for the domain. DMARC lives at _dmarc and DKIM at selector._domainkey.
- NS and SOA
- Which name servers are authoritative, and the zone's serial number and timers.
- CAA
- Which certificate authorities may issue certificates for the domain.
After a change, compare the three resolvers. When they agree, most visitors see the new record. If they do not, wait for the old record's TTL to run out.
Questions
What does a DNS lookup show?
The records that tell the internet where a domain lives: A and AAAA for the server addresses, CNAME for aliases, MX for mail servers, TXT for verification and email security (SPF, DKIM, DMARC), NS for the name servers in charge, SOA for zone settings and CAA for which authorities may issue certificates.
What is DNS propagation?
After you change a record, resolvers around the world keep serving the old answer until its time-to-live runs out. This tool asks Cloudflare, Google and Quad9 at once; when they agree, most people are seeing the new value.
Why don't the resolvers agree?
Usually a recent change that some resolvers still have cached, or a service that answers differently by location (CDNs and geo load balancers do this on purpose). Wait for the record's TTL to pass, then check again.
How do I check my email records?
Look up your domain for MX and the SPF line in TXT. DMARC lives at _dmarc.yourdomain.com and DKIM at selector._domainkey.yourdomain.com; enter those names directly.
Point your domain at a PrivateByte server: dedicated IPv4, reverse DNS you control.